Constraints on sentence priming in the cerebral hemispheres: effects of intervening words in sentences and lists.

This study explored the role of syntactic organization on semantic facilitation for target words presented to the right (R) and left (L) visual fields (VFs). Sentence and unstructured list primes were contrasted and, in each condition, the effect of intervening unrelated words on the durability of priming within each VF/hemisphere was investigated. Each prime contained a critical word which occurred Near (one intervening word) or Far (six intervening words) from the target word and was semantically related to it or a neutral control. It was hypothesized that, for word lists, facilitation for RVF target words would decrease with increasing distance between the critical and target words. For sentences no decrease in facilitation was expected for RVF targets. However, for LVF targets, facilitation was expected to decrease with distance both for sentences and lists with no greater priming for sentences than for lists. The results supported these hypotheses. Priming effects that spanned several intervening items were found only when the primes were well-structured, normal sentences and the target words were presented to the RVF. These results suggest that while word-level priming processes are available to both hemispheres, the left hemisphere makes greater use of message-level syntactic and semantic mechanisms for sentence comprehension.